What can we learn from the disrupted in schizophrenia 1 interactome: lessons for target identification and disease biology?

Emerging genetic and biological data strongly supports Disrupted in Schizophrenia 1 (DISC1) as a schizophrenia risk gene of great significance for not only understanding the underlying causes of schizophrenia and related disorders but potentially to open up new avenues of treatment. DISC1 appeared to be a very enigmatic protein upon the initial disclosure of its protein sequence. Though it contained some well-characterized protein domains, they did not reveal anything about possible function. Recently, the identification of its binding partners has revealed an incredible diversity of potential cellular and physiological functions. In an attempt to capture this information we set out to generate a comprehensive network of protein-protein interactions (PPIs) around DISC1. This was achieved by utilizing iterative yeast-two hybrid screens, combined with detailed pathway and functional analysis. This so-called 'DISC1 interactome' contains many novel PPIs and has provided a molecular framework to explore the function of DISC1. Interrogation of the interactome has shown DISC1 to have a PPI profile consistent with that of an essential synaptic protein, which fits well with the underlying molecular pathology observed at the synaptic level and the cognitive deficits seen behaviourally in schizophrenics. Furthermore, potential novel therapeutic targets have also emerged as we have characterized in detail the interactions with the phosphodiesterase PDE4B in collaboration with the Porteous and Houslay labs, and with Ndel1-EOPA with Hayashi and colleagues. Many components of the interactome are themselves now being shown to be schizophrenia risk genes, or to interact with other risk genes, emphasising the power of protein interaction studies for revealing the underlying biology of a disease.